Arduino Nano

Project

Goal: Create a physical interface to send keypresses to PC. So pressing a button labelled with 1 simulates a keypress "1" on PC.

The way it works is:

From Arduino side

  1. AnalogPin A1 is wired to button labelled "1"

  2. Arduino sets pin read mode to INPUT_PULLUP

  3. When push button is pressed, Arduino gets a LOW signal on that pin

  4. That pin is programmed to wirte to Serial buffer kb:1

    1. kb is a prefix, meaning keyboard

    2. : is just a delimiter

    3. 1 after the delimiter is the actual payload, ie data determining what button to simulate

From PC side

  1. Serial2Keypress is listening to Serial port

  2. it reads kb:1 and understands that the key needing to be pressed is 1

  3. Serial2Keypress simulates 1 keypress

Hardware List

  • Arduino Nanao

    • ATmega 328p microcontroller

  • Some breadboards and various length jumper wires

  • Cardboard and double sided tape

Arduino code

< Click here to see full code > 

// Analog pins
#define APIN_1 A1
#define APIN_2 A2
#define APIN_3 A3
#define APIN_4 A4
#define APIN_5 A5

// Digital pins
#define DPIN_2 2
#define DPIN_3 3
#define DPIN_4 4
#define DPIN_5 5
#define DPIN_6 6
#define DPIN_7 7
#define DPIN_8 8
#define DPIN_9 9
#define DPIN_10 10
#define DPIN_11 11
#define DPIN_12 12

const int writeDelay = 200;
const int amountOfPins = 16;

typedef struct {
    uint8_t pinId;
    char *keypress;
} Pin;

Pin pins[amountOfPins] = {
    {APIN_1, "1"},
    {APIN_2, "2"},
    {APIN_3, "3"},
    {APIN_4, "4"},
    {APIN_5, "5"},
    {DPIN_2, "6"},
    {DPIN_3, "7"},
    {DPIN_4, "8"},
    {DPIN_5, "9"},
    {DPIN_6, "0"},
    {DPIN_7, "a"},
    {DPIN_8, "b"},
    {DPIN_9, "c"},
    {DPIN_10, "d"},
    {DPIN_11, "e"},
    {DPIN_12, "f"},
};

char serialBuf[30];
const char *prefix = "kb:";
const char *newLineReturn = "\n\r";

// NANO EXCEPTION 1
// A6 and A7 can only be read as analog inputs
// NANO EXCEPTION 2
// D13 needs external resistor, because it's connected to
// onboard LED/cannot use INPUT_PULLUP

void setup() {

    Serial.begin(9600); // Setup Serial communication
    for (int i = 0, j = amountOfPins; i < j; i++)
    {
        pinMode(pins[i].pinId, INPUT_PULLUP);
    }
}

void loop() {
    for (int i = 0, j = amountOfPins; i < j; i++)
    {
        if (digitalRead(pins[i].pinId) == LOW) {
            strcpy(serialBuf, prefix);
            strcat(serialBuf, pins[i].keypress);
            strcat(serialBuf, newLineReturn);
            Serial.write(serialBuf);

            // clear char buffer
            strcpy(serialBuf, "");

            delay(writeDelay);
            break;
        }
    }
}

Media

Arduino Nano example 1
Figure 1. Arduino Nano example 1
Arduino Nano example 2
Figure 2. Arduino Nano example 2
Arduino Nano example 3
Figure 3. Arduino Nano example 3